Brake drum



C. W. DAKE BRAKE DRUM July 7, 1936.

Original Filed Jan. 15, 1934 mgmu fig 2.

Patented July 7, 1936 BRAKE DRUM Charles W. Dake, Grand to Campbell, Wyant &

Haven, lificln, assignor Cannon Foundry Company, Muskegon Heights, Mich, a corporation of Michigan Original application January 15, 1934, Serial No. 706,693. Divided and this application May 14,

1934, Serial No. 725,613

3 Claims.

This invention relates to a brake drum.

More particularly, this application claims the brake drum as an article and is a division of my patent granted December 11, 1934, No. 1,983,839.

One object of this invention is to economically produce a brake drum which will be eflicient in action. That is, the braking surface is non-porous and free from pitting or other defects and the outer periphery or the portion adjacent to the 10 braking band is of stronger metal as will be understood from the following specification.

An understanding of the invention and of the various objects enumerated, as well as others not at this time stated, may be had from the followl5 ing description, taken in connection with the accompanying drawing, in which,

Fig. 1 is a vertical section taken diametrically of an annular mold in which the drum, ring or flange is cast, the interior of the mold conform- 20 ing to the desired exterior form of the brake drum flange.

Fig. 2 is a section taken centrally through a brake drum produced in accordance with the present invention.

Like reference characters refer to like parts in the difierent figures of the drawing.

One form of apparatus with which the mold is used and by means of which the casting is formed is shown in Fig. 1. It includes a revolu- 30 ble spindle l having an annular flask I I mounted thereon and a mold I2 is positioned in the flask H. The upper part of the flask member ll is undercut as shown and retaining segments l3 hold the mold 12 in place.

A locating post It is provided interiorly of the spindle I 0 and locates the distributor l5.in position as clearly shown in Fig. 1. The molten metal l6, indicated indotted lines in Fig. 1, is poured from the ladle l1 and contacts against 40 the beveled edge of the distributor l and then enters the mold l2. As shown, the face of the mold I2 is corrugated to form ribs upon the brake drum indicated generally by the numeral 20.

The molten metal poured into the mold is an 45 alloy consisting preferably principally of two metal constituents; An example may be furnished by an alloy of iron and copper. The metal in a molten state and, preferably heated considerably above its melting temperature, is poured into 50 the rotating mold. Through centrifugal action the metal rises against and covers the inner substantially vertical face of the mold. It fills all of the grooves and depressions in the inner surface of the mold. The shaft l0 and the flask ll 55 attached thereto are rotated at high speed. A

peripheral speed of the molten metals of substantially 3000 feet per minute has the effect of causing the two metals of different specific gravity, cast iron and copper, to separate, the heavier metal going to the outside. If the speed is increased to a peripheral speed of the metals of 5000 feet per minute, there will be a very nearly complete separation of the copper and cast iron, whereby there will be produced a casting, the inner annular portion 20 of which is of cast iron, the outer annular portion 25, including the projecting annular ribs thereon, of copper and at the junction of the two, indicated by dotted lines at 26, there will be no sharp separation of the metals but an intermediate zone where the two are intimately mingled. This zone follows the outer contour of the drum and consequently has a cen tral bulge thereon. This bulge provides a reinforcing rib for the ring. Also, it increases the rate of heat transfer outwardly through the ring inasmuch as it increases the surface contact between the cast iron and the copper and the rate of heat transfer is dependent upon the size of the contacting surfaces. In practice the quantity of copper used should not exceed 15% of the mass of metal.

The temperature of the molten metal may range from 2300 F. to 3000 F. when an alloy of cast iron and copper is used as described. Copper melts at 1981.4 F. and cast iron from 1900 to 2200 F., depending upon the composition of the cast iron. At 230Q F. all of the metal will'be melted, and heated somewhat above melting temperature. Preferably. the temperature should be sufliciently above the melting point that the molten metals will remain in a freely fluid state for a period of time during the operation such that there can be ready separation under the centrifugal forces operating upon them, and there will not be too rapid a solidification such that any solidifying or thickening of the molten metals would interrupt the separation. In addition any gases, impurities, slag or the like should be enabled to pass with freedom through the molten metal to the inner surface of the ring casting and thus eliminate any possibility of defects, such as porosity or trapped slag or other impurities in g the cast iron which would detrimentally affect the braking surface of the cast iron after it has been machined at the inner curved surface of the casting produced. For these reasons the use of a temperature in pouring but little above the temperature at which the metals will be all melted is to be avoided, and considerably higher than mere melting temperature used.

The drum thus produced, using cast iron and copper as the metals, has an inner braking face of cast iron and an outer supporting shell of copper which is not brittle like cast iron but has the property of toughness and strength. The brake drum ring produced therefore combines the desired soft, yet positive braking characteristics of cast iron without the necessity of using an undue weight of metal which would be needed it cast iron alone was used, the copper shell pro viding the necessary toughness and tensile strength to insure the drum against breaking under shock.

As previously described the extent oi separation is governed by the rotative speed. The higher speeds, which produce a peripheral speed ot-substantially 5000 lineal feet per minute of the molten metal, are better than the lower speed or 3000 lineal feet per minute peripheral speed because of the greater separation of the cast iron and copper; and there will be proportionally greater or less separation as the speed is increased or diminished. What is the best speed for the particular article being manufactured may be determined by test and experience.

It is to be understood that while a specific example of two metals like cast iron and copper has been given the invention is in nowise limited to the use of such two metals alone. Other metals may be used together, that is, preferably other metals than copper with cast iron for brake drum purposes. And for other purposes wherein the inner material does not necessarily have to be of cast iron other suitable metal for the desired purpose may be used in its place. Such diflferent metals with their diflering specific gravities will require a speed of rotation in correspondence with the difierences in specific gravity. If the two metals are nearer'together in specific gravity than are copper and cast iron, the speed of rota:

tion will need to be increased. If they are farther apart in specific gravity the speed oi rotation can be reduced so as to get the desired efiective separation. It is further to be understood that while the temperature should preferably be considerably above the temperature at which the metals will be wholly molten, when cast iron is used as one of the metals and the other metal has a melting point like copper of substantially 2000 I". the compositionof the cast iron will be controlling as to its melting point, and the temperature of the composite mixture when poured into the mold 5 can be lower for a low temperature melting cast iron than for a high temperature melting cast iron. Also a high phosphorus content in cast iron renders the same much more fluid than one using low phosphorus content and the temperature to which the composite mixture of molten cast iron and copper is raised for pouring into the mold may be less with the high phosphorus iron than with the low phosphorus iron. It is for this reason that a temperature range from 2300 15 to '3000 F; has been speciiiced in order to cover the difl'ering characteristics of diflering cast irons as to melting points and fluidity after melting.

After the composite brake drum has been it may be supplied with a back 2| oi. wrought, 20 rolled or pressed steel which is welded or otherwise suitably secured to the ring as shown in Fig. 2. The annular flask l l is driven through the spindle III in any desired manner.

Having describedmy invention what is claimed 25 is: Y

1. In a brake drum, a braking ring of cast metal comprising an inner stratum of cast iron having a circumferential bulge on its outer surface, and an outer stratum of cast copper, said 30 copper and iron having an integrally cast con-- nection with each other.

2. In a brake drum, a braking ring flange oi. centrifugally cast metals having an inner peripheral layer of cast iron and an outer peripheral 35 layer of copper, the said iron and copper intermingling with each other forming a Joinder zone of iron and copper, said Joinder zone having a shape similar to the outer surface of the layer of copper.

3. A brake drum comprising a centrifugally cast annular braking member oi! ferrous metal having as its principal constituent iron into which is mixed copper in decreased quantity from its outer periphery inwardly, said outer periphery 5 being a stratum of copper.

' CHARLES W. DAKE. 

